We are using p-modulation doping to reduce the linewidth enhancement factor in Quantum Dot lasers. This is important for narrower linewidth lasers, lower chirping lasers and reduced reflection sensitivity lasers.

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This work reports on the ultra-low linewidth enhancement factor (aH-factor) of semiconductor quantum dot lasers epitaxially grown on silicon. Owing to the low density of threading dislocations and resultant high gain, an aH value of 0.13 that is rather independent of the temperature range (288 K–308 K) is measured. Above the laser threshold, the linewidth enhancement factor does not increase extensively with the bias current which is very promising for the realization of future integrated circuits including high performance laser sources.

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The aH-factor as a function of temperature for p-doped (red) and undoped (blue) QD lasers. The linear curve-fittings (dashed lines) are the guide to the eye only.